He doesn't, of course. He specifies almost nothing at all about the procedure, which is suspicious.
The qualitative description given in his June 18 affidavit is that it was "material needed to burn the bodies", and that "the bodies were drenched/covered with fuel/inflammable material". If we take this at its most favorable, we could suppose that the pit was filled with gas such that the bodies were actually immersed in it. Putting aside whether this is a reasonable use of fuel during wartime, would it actually work for cremation?